SIY3.TXT Field Survey and Write a Land Description 21 Chapter 3 Field Survey and Write a Land Description In this chapter you will write a land description just like you did in Chapter 2. The only exception is that you will do it from a map on a grand scale. The real Earth. For this chapter you will need: a) Silva Ranger type 15 compass, available for $40 from CAVE Inc, 1/2 Fast Road, Ritner, KY 42639. 606/376-3137. This time there is no substitute for the real thing. b) A place outdoors to practice, c) Pencil and notepaper. You will not need: a) Tapemeasure, but when you do need one, an unbreakable 200 foot Keson PVC coated fiberglass surveyor's tapemeasure is available from CAVE Inc for $28. b) Clinometer, c) Assistant, d) Deed. e) You don't even need this computer, except to make a printout so that these instructions can be doodled with a pencil. You will be doing something different with the compass. You will use it for a compass. Put the compass on like a necklace with a pendant. The latest fad. Open the compass lid. Tilt the mirror up about halfway towards straight up. Hold the compass out in front of you, at about mouth level. Close one eye and sight your target thru the vee sighting notch atop the mirror. Now look into the mirror, without moving the compass. Twiddle with the mirror until you can see all of the compass dial in the mirror. Don't try to look at the compass dial directly. You can't see the dial and still hold the compass level, so don't bother trying. The compass must be level when taking a compass direction. The compass needle must be free to swing and jiggle without binding on the compass case. SIY3.TXT Field Survey and Write a Land Description 22 There is a line in the mirror. Turn the compass until this line goes thru the pivot point of the compass needle. Now turn the dial until the red and black arrow lines up with the compass needle. The needle red and the arrow head. The old Ranger has an all black arrow, but don't let that confuse you. Note that the needle may not be exactly in the center of the red and black arrow. That's OK, just so long as the needle and the sides of the arrow are parallel. Your compass direction is under the index blob. And it will stay there until you change it. Read the compass direction at your leisure. To take a good compass reading, the following four things must all happen at the same time. In what order you do them makes no difference, as long as they all finally happen at the same time. a) You see your target thru the vee sighting notch. b) You see the line in the mirror pass thru the center of the needle pivot. c) You see the red and black arrow and the compass needle align. Needle red, arrow head. d) The compass needle really is pointing North. Now that you know how to take a compass reading, find yourself a place to work outdoors. A yard or park is the best choice. It needs to be level and at least 25 paces square. A pace is how far you get in one step. About 2.5 to 3.0 feet. Try to find a place without too much traffic or interruptions. Pick an obvious place to start. Try to keep away from steel. Steel perturbs the compass. Stay 5 paces away from cars, steel reinforced pavement, or wire fences. I don't know how far from a steel reinforced building is dangerous, never having had that problem. 50 paces?? Label your paper with headings: TO FROM COMPASS TAPE COMMENTS Your starting point is station 0. Describe or mark it so that you can find it again. You'll know if you have done a good job of marking it when you try to find it again. Enter the data for this station in your notes. A row of 0 0 0 0. Remember, you gotta start somewhere. Pick your next station. It is the second station, but name it "1". This one need not be permanent. A wad of paper, a beer can, or an assistant will do. Just so long as it stays put for a few minutes & you can see it from station 0. Go back to station 0. Measure the COMPASS direction TO station 1 FROM station 0. Sight thru the vee sight, put the line in the mirror in the center of the pivot, and turn the arrow until it aligns with the compass needle. SIY3.TXT Field Survey and Write a Land Description 23 The arrow head and the needle red. Check that the compass isn't tilted so that it binds the needle. Now pace off the distance to station l from station 0. Enter this information in your notes. I hope that you don't feel that I have cheated you, but that's all there really is to land surveying. If you are really dissatisfied, I'll refund your money. What can I say? I told you that this was ridiculously easy. For the rest of you, there are a lot of helpful hints. Organize your data notes the same way as you did in Chapter 2. TO FROM COMPASS backsight TAPE COMMENTS Record your data for each station. Be sure that you have recorded the data for each line before you move on to the next station. And always be sure to start somewhere. You can check your compass technique by taking a compass direction to station 0 from station 1. If you align the tail of the arrow with the red end of the compass needle, you can read your original compass direction under the index blob. No need to fool around adding 180 degrees. This is a backsight. You took the compass direction to station 0 from station 1. What you really wanted was the direction to station 1 from station 0. These directions are 180 degrees apart. You were heading in exactly opposite directions. Be careful that you don't make the classic blunder of getting them mixed up. Everybody has to do it once. Record backsights in the backsight column. Notice that when you are standing on station 1 looking at station 2, your compass reading is TO 2. When you look back to station 0, your backsight is TO 1. They are not entered on the same line. With a little practice you should be able to get your sights and backsights to agree within a degree. For now, five degrees difference is plenty good enuf. You might not be able to agree even within five degrees if you are near a lot of steel. If you have this problem, then try a different yard or park before yelling for help. The distance is measured in paces. Just walk between the stations and count your steps. Measure to half paces. If you want to know the distance in feet, you will have to measure the length of your pace in feet for a conversion factor. SIY3.TXT Field Survey and Write a Land Description 24 Your pace should be about 2.5 to 3.0 feet. By the definition of a mile (a thousand double paces) it is 2.64 feet [5280 / 2000, where the symbol "/" is computerese for the arithmetic operation of divide]. You could use your tapemeasure if it won't cause a traffic jam. You should now have two stations recorded. Station 0, your starting station, and station 1, with compass and tape data. Pick station 2, put something there so that you can see it from station 1, and go to it. Put in station 3. Now put station 4 in the same place as station 0. Make a note in your comments that station 4 is the same place as station 0. Your now have four stations in a loop. The closure error on the ground in reality is 0.0 Stations 0 and 4 are in exactly the same place. Pick up your trash and go back to your kitchen table, or whatever you are using for an office. Get out a fresh sheet of notepaper. Transcribe your field notes. Make a nice clean office copy without all the doodles and crossed out mistakes. (You've already found out that erasures of bad data are an invitation to blunder. Cross out those mistakes.) Be sure to label both the field and office copies with what you have surveyed, when, with what instruments, and by whom. Now plot a map from your data. Just like you did in Chapter 1. Be sure that you label your map. Be sure that the North arrow points up. A Suggested scale is 10 paces per inch. Write on your map: "10 paces = 1 inch" (or whatever scale you are using). This is so that you will remember the map scale tomorrow. You should have a closure error of a few paces. If you wish to get more technical, you should not have more closure error than 2 paces plus 5% of the run. If you do have more error than this, it is not error. It is blunder. Go survey it again and find out what you did wrong so that you don't make the same mistake again. If you do make the same mistake again, try a different place. The most likely problem in a city is too much steel perturbing the compass. How well do your sights and backsights agree? Now find a place where you can try the 200 foot surveyor's tapemeasure. Note that the tapemeasure is graduated in feet and tenths, not inches. This makes the calculations a lot easier. I like to call TAPE by the name PACE when I'm doing a pace survey. That makes it easier to understand my notes later. SIY3.TXT Field Survey and Write a Land Description 25 If you can't find a convenient place to use the tapemeasure, just continue. Play with the tape when you find a safe place. If you wish, you can plot your map at the same time as when you collect your survey data. Your protractor is already set to the proper direction. The ruler is right there in your hand too. This is the great advantage of the Silva Ranger over other systems. Replot your field map when you get back to your kitchen office. Plotting as you survey helps you to keep track of what you are doing, and catches blunders. All this time you have assumed that the compass needle was pointing North. It wasn't, but it was close. The compass doesn't point towards The North Pole, but rather to The North Magnetic Pole. Adjust the declination on your compass. Turn the declination adjusting screw located at 45 degrees on your dial. Use the screw driver on the safety cord. Read the declination under the tail or head of the black arrow. It doesn't make any difference which end of the arrow you use, but you might understand better which way is which if you use the arrow head as the declination pointer. Even Silva gets confused when they try to set declination on the south! The Silva instructions have a map of the United States of America with the declinations marked. Or look on a topographic map. Or ask your local Geological Survey. Note that if you move a hundred miles or so east-west, you must readjust the declination. Declination also changes with time. I usually set the declination to 0.0 and correct the compass with my computer program. If I bother to correct it at all. The declination read from the Silva instructions will be plenty good enuf for you. Steel objects perturb the compass. I can't say it often enuf! Cars, fences, axes, guns, knives, motors, buildings, steel reinforced pavement, and maybe even your eyeglass frames, jewelry, wristwatch, or pacemaker will affect the compass. When in doubt, test. See how close to the compass needle the object must be before the needle is affected. Then at least triple it for safety. For a movable object, have an assistant move it around while you watch the compass needle. For an immovable object, sight on a distant target, then move along the line of sight away from the test object and take another compass reading. If you were far enuf away, the compass reading will not change. Some places have magnetic rocks which disturb the Earth's magnetic field which your compass is sensing. If this is the case, then you are out of luck. Such places are usually in areas of mining activity or of metamorphic rock. You can't survey with a compass in Lodestone Gulch nor on Magnetic Mountain. SIY3.TXT Field Survey and Write a Land Description 26 Silva claims that their sealed liquid filled compass capsule resists static electricity interference. I never heard of static electricity affecting a compass, but the magnetic field created by direct current sure does. There is no resistance possible either, since it is the magnetic field which is perturbed. The compass aligns with the perturbed field just like it is supposed to do. Sloppy technique is another problem. The Ranger is much more accurate when used on the lanyard than when held freehand. Be sure that the compass is pulled to the end of the necklace. This both steadies it and keeps it in the proper position. If the target is almost in the vee sighting notch, or if the mirror line is almost in the center of the needle pivot, or if the arrow and the compass needle are almost aligned, then you will get almost the correct compass direction. The worst problem with the Silva Ranger compass is not getting the compass level. You can have an assistant check this for you, or you can check it yourself. Tap the side of the mirror with your finger. The needle should jiggle and return to the same place. If the needle is not free to jiggle, then the compass is tilted and you will get the wrong compass direction. Another trick is to flop the compass over on its side, then sight it again. The needle and the arrow should line up again. Perfectly. You should try surveying in the park a few times so that you make most of the normal beginner's blunders in a safe place. If you have questions or comments, contact me. Dave Beiter CAVE, Inc 1/2 Fast Road Ritner, KY 42639 606/376-3137